Waikoloa Reservoir No. 1
Waikoloa Reservoir No. 1 is an earth dam located in Hawaii County, Hawaii, built in 1970. It carries a High hazard potential classification and has a poor condition assessment.
About Waikoloa Reservoir No. 1
The primary purpose of Waikoloa Reservoir No. 1 is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Hawaii County, Dept Of Water Supply (local government). It impounds the Waikoloa-offstream near Waimea.
The dam stands 44 feet tall and stretches 1,700 feet across, creates a reservoir covering 6 acres, has a maximum storage capacity of 190 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1970, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 01/23/2025.
At 44 feet, this dam is taller than 90% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Hawaii dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Hawaii |
| County | Hawaii |
| Nearest City | Waimea |
| River/Stream | Waikoloa-offstream |
| Coordinates | 20.03812, -155.67247 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 44 ft |
| Dam Height | 44 ft |
| Dam Length | 1,700 ft |
| Year Completed | 1970 (56 years old) |
Storage & Hydraulics
| NID Storage | 190 acre-ft |
| Max Storage | 190 acre-ft |
| Normal Storage | 157 acre-ft |
| Surface Area | 6 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 160 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Hawaii County, Dept of Water Supply |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 01/23/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | HI00040 |
| Federal ID | HI00040 |
| More Info | State Dam Safety Program |